Generally, migration of a file system involves copying the file system located on a source block device, such as a disk partition, of a source device to a destination block device of a destination device and reproduce the file system. The block devices may also include, for example, a logical disk or a logical volume.
During file system migration, the file system may be modified at the destination block device. Modifications to the file system may be made for various purposes, for example, to ensure storage consolidation, to make space available for future storage, and to achieve effective disk space utilization. There may be certain modifications, such as downsizing of the file system, which may not be achievable at the destination block device. Such modifications of the file system may be carried out at an intermediate storage device between the source block device and the destination block device, or at the source block device.
Generally, there is no intermediate storage device available during file system migration, even on a temporary basis. In addition, the source block device may be placed in a quiesced state, i.e., a state where access to the file system on the source block device is available for read-only purposes and no modification to the file system can be made on the source block device. The source block device is placed in such a state to maintain consistency and integrity of the file system at the destination block device with reference to the source block device.